CMC/PEG containing hydrophilic denture adhesive

ABSTRACT

An improved denture adhesive containing sodium carboxymethylcellulose (CMC) as the sole adhesive component in a hydrophilic vehicle comprising certain polyethylene glycols (PEG) and, as an optional component in certain forms of the subject adhesives, glycerin, for enhancing pharmaceutical elegance of the final product.

This is a continuation of application Ser. No. 403,090 filed July 29,1982, now abandoned.

A highly effective hydrophilic denture adhesive composition is providedcomprising a substantially anhydrous mixture of from about 25 to about50 percent by weight of the total composition (i.e. w/w) of sodiumcarboxymethylcellulose as the sole adhesive component and a hydrophilicvehicle comprising from about 50 to about 75 percent w/w of apolyethylene glycol fraction with average viscosity of from about 44 toabout 25,600 centipoises at about 60° C. Various forms of the subjectcompositions are available, for example, liquids, creams and powders.Optionally, up to about one-half of the polyethylene glycol fraction maybe substituted with glycerin in the non-powder forms of the subjectcompositions. The denture adhesive composition may also have presentcolorants, flavoring agents, odorants, sweeteners and other additives inamounts generally employed for their respective intended purposes.

BACKGROUND OF THE INVENTION

Denture adhesive cream formulations have heretofore been comprisedmainly of natural or synthetic polymeric adhesives suspended in ananhydrous oleagenous vehicle system generally consisting of mineral oiland/or petrolatum. These hydrophobic formulations have viscositiesranging from moderately thick to very thick making them difficult tosqueeze out evenly and fluidly from the generally employed collapsibletubes or containers. However, this thickness range is necessary toprevent syneresis (i.e., phase separation) from occurring due to thesolid adhesive particles being only suspended in the hydrophobicvehicle.

More recently, liquid denture adhesives have been reported containingsodium carboxymethylcellulose and ethylene oxide homopolymer as thesolid adhesives suspended in mineral oil (e.g. see U.S. Pat. No.4,280,936). Examples of such hydrophobic denture adhesives are theproducts commercially available from Block Drug Company, Inc. in theUnited States under the trademark "Dentrol" and in West Germany underthe trademark "Cedenta", which are believed to contain about 41-45% w/wof sodium carboxymethylcellulose and ethylene oxide homopolymer in amineral oil base. However, upon standing, considerable phase separationoccurs thus requiring a "shake well" indication on the container.

Furthermore, whereas such formulations may be effective in securingdentures quickly within the oral cavity, it may be necessary to applymore than one application per day to obtain sufficient adhesionthroughout the day, depending on the fit of the denture and thepsychological need of the denture wearer. Such multiple applications areinconvenient and at times impractical or impossible and. therefore,these heretofore known denture adhesive liquids are not totallyacceptable and in some cases undesirable.

Whereas these conventional types of denture adhesive creams and liquidshave provided good stabilizing/hold properties to denture wearers, someorganoleptic negatives have also been perceived with these products.Some of these commonly perceived negatives are, for example, unpleasantmouth feel, bad taste, grittiness, oily sensation in the mouth anddifficulty of application and removal from dentures. Anotherdisadvantage is that the salivary fluids have to penetrate a hydrophobicvehicle in order to reach and hydrate the adhesive system. Thishydrophobic barrier may cause a time lag before the adhesive is hydratedand starts to work. Due to such slowed rate of hydration of adhesivecomponents, there results a lack of immediate denture hold.

It has therefore been desirable to provide a denture adhesive ofsuperior adherent properties over prolonged periods of time. Such isaccomplished with the denture adhesive compositions herein described, anovel and unique combination of an adhesive in a hydrophilic vehiclesystem which eliminates many of the aforementioned disadvantages foundwith denture adhesives having conventional oleagenous vehicle systems.For example, the hydrophilicity of this unique combination facilitatesthe penetration of the saliva to the adhesive gum system, therebyallowing quicker hydration, and, therefore, quicker hold. Test resultshereinafter demonstrate the stronger hold of the subject compositions.Furthermore, they are available in forms with variable consistencies,for example, liquids, creams and powders.

In our copending application Ser. No. 361,631 filed Mar. 26, 1982entitled "Hydrophilic Denture Adhesive", the use of a polymeric adhesivesystem comprising sodium carboxymethylcellulose in admixture with anethylene oxide homopolymer in specified ratios together with ahydrophilic PEG vehicle was described. In contrast, the instantcompositions eliminate the need for said ethylene oxide homopolymer andutilize sodium carboxymethylcellulose as the sole adhesive component.

DETAILED DESCRIPTION OF THE INVENTION

This invention relates to a hydrophilic denture adhesive compositionwhich, when in contact with saliva, hydrates within the oral cavity toprovide superior adherent properties. The composition comprises twoessential components. The first is from about 25 to about 50 percent w/wof sodium carboxymethylcellulose as the sole adhesive ingredient. Thesecond is a hydrophilic vehicle comprising from about 50 to about 75percent w/w of a polyethylene glycol fraction with average viscosity offrom about 44 to about 25,600 centipoises when measured at about 60° C.,generally 60° 2° C.

With regard to the adhesive component, sodium carboxymethylcellulose iswell known and commercially available. It is a powder which, whenmoistened, becomes hydrated and tacky or gummy in consistency withadhesive characteristics. The sodium carboxymethylcellulose "gums"employed in this invention are water soluble, anionic, long chainpolymers, derived from cellulose. Properties vary with the averagenumber of carboxy methyl groups that are substituted per anhydroglucoseunit in each cellulose molecule. This property is generally referred toas "the degree of substitution", with the maximum substitution possibledesignated as "3.0" since there are just three hydroxy groups capable ofreaction in each anhydroglucose unit. For the practice of thisinvention, it has been found that one or more such cellulose gums havinga degree of substitution of from about 0.4 to about 1.2 is suitable. Theviscosity of a 1 percent solution of the gum, measured at 5° C., shouldbe in the range of from about 400 to 4,500 preferably 1,500 to 2,500centipoises.

Sodium carboxymethylcellulose gums of this type are more fully describedin "Chemical and Physical Properties: Cellulose Gum," 1978, published byHercules, Incorporated, Coatings and Specialty Products Department, 910Market Street, Wilmington, Del. 19899.

As examples of commercially available sodium carboxymethylcellulose gumssuitable for use in this invention there may be mentioned those sold byHercules, Incorporated, Wilmington, Del. as types 4H1, 7H, 9H4, 7H3S,7H0F and 7H4. Type 7H3S is preferred for use in this invention.

In the compositions of this invention, the adhesive component comprisesfrom about 25 to about 50 percent w/w and preferably from about 35 toabout 45 percent w/w of sodium carboxymethylcellulose.

With regard to the hydrophilic vehicle component, the polyethyleneglycols suitable for use in the compositions of the invention are alsowell known and commercially available, for example, those marketed byUnion Carbide Corporation under its trademark "Carbowax".

Polyethylene glycols are polymers of ethylene oxide with the generalizedformula HOCH₂ (CH₂ OCH₂)_(n) CH₂ OH wherein n represents the averagenumber of oxyethylene groups. These polyethylene glycols, which aredesignated by a number that represents the average molecular weight,range from clear viscous liquids at room temperature (e.g., PEGs 200,300, 400 and 600) to soft solids (e.g, PEGs 1000 and 1450) to waxysolids available in the form of flakes or powders (e.g., PEGs 3350 and8000) to granular solids (e.g., PEG 14,000). All these polymers dissolvein water to form clear solutions and this water solubility featureimparts a hydrophilic characteristic to the compositions of thisinvention.

The subject compositions comprise from about 50 to about 75 w/w andpreferably from about 55 to about 65 percent w/w of a polyethyleneglycol (PEG) fraction with an average viscosity when measured at about60° C. of from about 44 to about 25,600 centipoises (cps), preferablyfrom about 44 to about 2,500 cps, and most preferably from about 44 toabout 300 cps, as determined, for example, by an instrument such as theBrookfield RVT Viscometer. Either individual polyethylene glycols orblends of two or more polyethylene glycols within this viscosity rangemay be utilized. For example, and without being limited thereto, a blendof liquid PEG 400 or PEG 600 and solid PEG 8000 in a respective weightratio of from about 9:1 to about 33:1, has been found particularlysuitable for the lotion-like liquids and soft creams of this invention.

The data presented in following Table 1 illustrats the variety of finalproduct consistencies obtainable according to this invention by varyingthe make-up of the PEG fraction in a particular formulation. In Example4 hereafter, a formulation is described which contains 45% w/wNa-carboxymethylcellulose, 10% w/w glycerin and 44.69% PEGs, the lattermade up of PEG 400 and PEG 8000 in an approximate 9:1 ratio,respectively. By substituting an equivalent amount of total PEG but inthe indicated varying ratios, the following results are approximated.

                  TABLE 1                                                         ______________________________________                                        Vehicle Ratio                                                                             PEG Fraction                                                      (PEG 400:   Viscosity      Product                                            PEG 8000)   (cps @ 60° C.)                                                                        Consistency                                        ______________________________________                                        100:0       56             liquid lotion                                      98:2 (49:1) 44             liquid lotion                                      97:3 (32.3:1)                                                                             61             liquid lotion                                      94:6 (19:1) 72             liquid lotion                                      92:8 (11.5:1)                                                                             94             liquid lotion                                      90:10 (9:1) 94             soft cream                                         80:20 (4:1) 170            cream                                              70:30 (2.3:1)                                                                             315            thick cream                                        60:40 (1.5:1)                                                                             600            very thick cream                                   0:100 (PEG 8000*)                                                                         2,500          powder                                             0:100 (PEG 14000*)                                                                        25,600         powder                                             ______________________________________                                         *The 10% w/w glycerin replaced by an equal amount of PEG.                

By blending members of the PEG series, different viscosities within thedefined range may be obtained, as desired. For example, by utilizingincreasing amounts of higher molecular weight PEGs, i.e. more solidsthan liquids, the resultant viscosity of the polyethylene glycolfraction will also increase (assuming other ingredients in the dentureadhesive composition are maintained constant) so that one can readilyobtain embodiments of the subject compositions ranging in consistencyfrom viscous liquids to creams to powders. For example, with about 32percent w/w of the sodium carboxymethylcellulose adhesive and 10 percentw/w of glycerin, a polyethylene glycol fraction having a viscosity atabout 60° C. of about 44-95 cps affords a final product with a liquidlotion to soft cream consistency; whereas a polyethylene glycol fractionhaving a viscosity of about 100-300 cps affords a cream type of finalproduct, whereas a polyethylene glycol fraction above 300 affords athick creamy product and whereas without glycerin a polyethylene glycolfraction having a very high viscosity of about 2500-25,600 cps affords afinal product in powder form.

This ability to adjust the fluidity of the final product is aparticularly advantageous feature of the invention since it affordscommercialization of final product forms with consumer acceptableconsistencies such as (i) liquids and soft creams, which are readilyextrudable from appropriate containers, for example, pump actionbottles, squeezable tubes and the like, (ii) thicker creams and (iii)powders, all of which forms are suitable for easy application todentures.

With regard to the liquid and cream compositions of this invention, oneparticular ingredient that is preferred and recommended as a substitutefor part of the polyethylene glycol fraction is glycerin which has aknown soothing effect on oral gum tissue and also affords a pleasantmouth feel and sweetening taste to the finished composition. Due to itshumectant character, glycerin also contributes to the hydrophilicity ofthe finished composition, thereby allowing quicker hydration on contactwith moisture or saliva. Thus, although glycerin is not an essentialcomponent of the hydrophilic vehicle or of the finished composition, itdoes enhance the latter's esthetic appearance and acceptability.

It has been found that a significant amount of glycerin can besubstituted for the polyethylene glycol fraction, for example, up toabout one-half of the latter may be so substituted without anysignificant detriment to the overall adhesive ability of the finishedcomposition. However, due to the increased cost incurred with highamounts of the relatively expensive glycerin, about 25% w/w of glycerinis recommended as the upper limit with about 5 to about 15 percent w/wbeing preferred and about 10 percent w/w most preferred.

Any suitable flavoring agent, colorant, odorant, natural or syntheticsweetener, deodorant, antimicrobial agent, tissue healing agent or otheroptional ingredient generally employed as an additive in dentureadhesives may be utilized in the compositions of this invention, if sodesired, so long as such addition is not detrimental to the overalladhesive ability of the compositions. Preferably, up to about 1.0% w/wof such additives may be utilized.

Typical of the compositions encompassed in the present invention are theformulations exemplified in Table 2. The symbol "% w/w" indicates theweight of each ingredient based on the total weight of the particularcomposition.

                  TABLE 2                                                         ______________________________________                                        Formulation Examples in % w/w                                                           Ex. 1  Ex. 2    Ex. 3    Ex. 4                                      ______________________________________                                        Na--carboxymethyl-                                                                        50.0     25.0     35.0   45.0                                     cellulose                                                                     PEG 400                              40.0                                     PEG 600     50.0     75.0                                                     PEG 8000                      65.0   4.59                                     Glycerin                             10.0                                     Color: FD & C Red                    0.01                                     No. 3                                                                         Flavor: Premix                       0.4                                      of mint oils                                                                  Total % w/w 100.0    100.0    100.0  100.0                                    Form:       lotion   lotion   powder soft cream                               ______________________________________                                    

The compositions of this invention can be produced by standardcompounding techniques. For example, the liquid and cream compositionsare readily prepared by heating with stirring the polyethylene glycolfraction to about 65°-70° C. at which temperature any solid orsemi-solid polyethylene glycols which may be present are liquified andthe fraction has a syrupy gel-like consistency. The sodiumcarboxymethylcellulose is added to the polyethylene glycol fraction,slightly cooled to about 50°-55° C., with constant stirring to obtain auniform adhesive/vehicle mixture. Any optional additives such as flavor,color and the like may then be incorporated into the adhesive/vehiclemixture. It is recommended, however, that the adhesive/vehicle mixturebe cooled to about or slightly below 40° C. before incorporation of anysuch additives of a volatile character, for example, aromatic flavors,in order to preserve their characteristic essences.

When glycerin is to be included in the final product, it isadvantageously added to and mixed into the slightly cooled (about50°-55° C.) polyethylene glycol fraction prior to admixture with theadhesive component. The glycerin addition step may also be utilized as away of carrying any compatible optional additive such as a sweetener,colorant and the like into the final product by simply mixing ordissolving the desired additive in the glycerin beforehand.

The powder compositions of this invention are readily obtained by simpleadmixture of the sodium carboxymethylcellulose powder with the powderPEG fraction of the hydrophilic vehicle component. The preferredpolyethylene glycol for making the powder compositions is PEG 8000alone. It is recommended that granular forms of polyethylene glycol,such as PEG 14,000 be pulverized to a fine powder prior to admixturewith the sodium carboxymethylcellulose.

The denture adhesive compositions of this invention possess superior andunexpected adhesion/cohesion properties as measured by the Texturometerevaluation test. The term Texturometer is a trademark for an instrumentmanufactured and sold by C. W. Brabender Instruments, Inc. ofHackensack, N.J. which enables a quantitative measurement of texturalparameters of products. The instrument mechanically simulates thechewing motions of the human jaws. A plunger is driven through the testsample (approx. 3 ml) held in a sample holder under which there is astrain-gauge hooked up to a high-speed chart recorder. The instrumentdraws force-time curves which are indicative of the cohesive/adhesiveability of the test sample. The plunger is driven through the testsample at the rate of 12 times per minute and the chart paper speed is1500 mm per minute.

The test sample is prepared by uniformly mixing the product to be testedwith distilled water in a small mortar and pestle at a ratio of one partby weight of product to four parts by weight of water. The areas underthe cohesion and adhesion parts of the force-time curves are measuredand these areas are a measure of the cohesive/adhesive abilities of thehydrated adhesive formulation, i.e., the larger the areas, the greatersuch abilities. After the initial measurement, the test sample is keptundisturbed in a tightly covered petri-dish (to prevent evaporation) for5 hour at 25° C. and then retested. Accordingly, in Table 3 hereafter,the tabulated numbers indicating the observed Texturometric evaluationsrepresent areas under the cohesion/adhesion Texturometric curves.

The unexpected superiority of the compositions of the present inventionis demonstrated by the Texturometer evaluation data set forth in Table 3wherein the compositions of Examples 1 and 2 are tested and comparedwith a conventional commercial product available under the brand name"Dentrol" which has a hydrophobic mineral oil vehicle rather than thehydrophilic PEG vehicle of this invention. The adhesive/cohesiveproperties of the tested hydrated products and evaluated initially andagain after 5 hours.

                  TABLE 3                                                         ______________________________________                                        Texturometric Evaluations*                                                            COHESION     ADHESION                                                         (sq. mm.)    (sq. mm.)                                                Test              After            After                                      Product   Initial 5 Hours    Initial                                                                             5 Hours                                    ______________________________________                                        Dentrol   279     568        71     37                                        Ex. 1     1230    2727       80    241                                        Ex. 2     548     922        227   214                                        ______________________________________                                         *Numbers represent areas under cohesion/adhesion Texturometric curves.   

The data listed in Table 3 shows clearly the unexpected and superiornature of the cohesion and adhesion parameters obtained withcompositions of this invention. Particularly noteworthy is the markedcohesion and adhesion abilities of the subject compositions even after 5hours. In contrast, the measured adhesion of the comparative commercialproduct decreased significantly, almost 50% after 5 hours. This markedcohesion and adhesion after keeping for 5 hours, characteristic of thesubject compositions, is even more surprising since it might be expectedthat with passing of time the water of hydration, considering thehydrophilicity of the subject compositions, might weaken rather thanstrengthen the structure of such compositions.

When in contact with moistened denture plates, gums and saliva, thesubject compositions hydrate within the oral cavity to provide superiordenture stabilizing properties not possessed by heretofore known dentureadhesives, the latter generally having hydrophobic vehicles for theadhesive components rather than hydrophilic vehicles as with the subjectcompositions. In general, furthermore, the subject compositions willform a clear gel-like mass (upon mixing with water or saliva) whereasconventional products with hydrophobic vehicles form an opaque, veryoily mass. Esthetically, the clear gel-like mass is more acceptable tothe user.

What is claimed is:
 1. A denture adhesive composition consistingessentially of a substantially anhydrous mixture of from about 25 toabout 50 percent w/w sodium carboxymethycellulose as the sole adhesivecomponent and from about 50 to about 75 percent w/w of a polyethyleneglycol fraction comprising one or more polyethylene glycols each havingan average molecular weight of from 200 to 20,000 and said fractionhaving a viscosity of from about 44 to about 25,600 centipoises at about60° C.
 2. A denture adhesive composition consisting essentially of asubstantially anhydrous mixture of from about 35 to about 45 percent w/wsodium carboxymethylcellulose as the sole adhesive component and fromabout 55 to about 65 percent w/w of a polyethylene glycol fractioncomprising one or more polyethylene glycols each having an averagemolecular weight of from about 200 to 20,000 and said fraction having aviscosity of from about 44 to about 2,500 centipoises at about 60° C. 3.A denture adhesive composition consisting essentially of a substantiallyanhydrous mixture of from about 25 to about 50 percent w/w sodiumcarboxymethylcellulose as the sole adhesive component and from about 50to about 75 percent w/w of a polyethylene glycol fraction comprising oneor more polyethylene glycols each having an average molecular weight offrom 200 to about 20,000 and said fraction having a viscosity of fromabout 44 to about 300 centipoises at about 60° C.
 4. The composition ofclaim 3 wherein said polyethylene glycol fraction comprises a mixture ofPEG 400 and PEG 8000 in a weight ratio of from about 9:1 to about 33:1,respectively.
 5. The composition of claim 3 wherein said polyethyleneglycol fraction comprises a mixture of PEG 600 and PEG 8000 in a weightratio of from about 9:1 to about 33:1, respectively.
 6. The compositionof claim 3 wherein up to about one half of said polyethylene glycolfraction is substituted with glycerin.
 7. A denture adhesive compositionconsisting essentially of a substantially anhydrous mixture of fromabout 25 to about 50 percent w/w of sodium carboxymethylcellulose as thesole adhesive component, up to about 25 percent w/w of glycerin, andsubstantially the remainder of a polyethylene glycol fraction comprisingone or more polyethylene glycols each having an average molecular weightof from 200 to 20,000 and said fraction having a viscosity of from about44 to about 300 centipoises at about 60° C.
 8. The composition of claim7 wherein said polyethylene glycol fraction comprises a mixture of PEG400 and PEG 8000 in a weight ratio of from about 9:1 to about 33:1,respectively.
 9. The composition of claim 7 wherein said polyethyleneglycol fraction comprises a mixture PEG 600 and PEG 8000 in a weightratio of from a 9:1 to about 33:1, respectively.